This invention relates generally to improvements in packing case members and more specifically to improvements in the coolant circulation structure of such members.
Broadly speaking, packing case structures have long been used in the prior art to provide a seal along and around a reciprocally movable piston rod of a gas compressor to prevent the escape of gas from the piston cylinder along and around the surface of the piston rod. Such packing case structures have also been used in the prior art to provide gas tight seals along and around the movable shafts of rotating machinery. Typically, a prior art packing case member or packing cup is cylindrically shaped and contains a central circular opening for stationary mounting in a compressor housing on a reciprocally movable piston rod. The central opening is of somewhat greater diameter than that of the piston rod so that the peripheral defining wall of central opening is spaced from the surface of the piston rod so that the latter does not rub against the cup as the piston rod reciprocates in the central opening. But since this spacing can allow gases being compressed by the piston to escape the compression chamber along and around the surface of the rod, the series of cups making up the packing case contains seal rings which slidably bear against the rod to provide a gas tight barrier.
The seal rings cause sliding friction to occur along the piston rod as the latter reciprocates through the former, which friction causes heating of the packing cups. While a liquid lubricant is typically introduced through a passageway in the packing case to the surface of the piston rod to reduce such sliding friction, enough friction usually remains to cause serious heating of the packing cups. To deal with this problem in the prior art, the cylindrically shaped cups are typically cast in two mating cylindrically shaped pieces. A circular groove is machined into opposing surface portions of the mating faces of the pieces so that, when they are joined, a circular passageway is formed in the cup housing which extends around a majority peripheral portion of the central opening. One end of the passageway contains an inlet port which opens onto one flat face of the cup, while the opposite end portion of the passageway contains an outlet port which opens onto an opposite flat face of the cup. A fluid coolant introduced into the circular passageway flows between the inlet and outlet ports to absorb heat from the cup housing.
Typically, a single inlet line carrying liquid coolant is connected to each inlet port in the series of cups making up a packing case. Similarly, a single outlet line collects the coolant circulated through each cup and is connected to each of the outlet ports of each of the cups. This arrangement is called parallel flow and has the disadvantage that the passageways of one or more cups can become clogged with incrustation or debris to produce increased heating in the clogged cup or cups without it becoming immediately apparent to operators of the compressor.
Another problem encountered with these prior art packing cups is that, because they are formed of two mated pieces, it is necessary to completely remove them from the piston rod and break them apart in order to clean the individual grooves forming the circular coolant passageways. A further problem results from having to form concentrically spaced apart annularly extending grooves in at least one of the mating pieces of housing, which grooves extend around opposite sides of the coolant passageway and in which a pair of O-rings can be placed to be confined between the mating surfaces of the pieces. This is necessary to inhibit coolant from leaking from the passageway between the mating pieces and out of the packing cup. But the O-rings and their grooves take up valuable space in the cup and thus limit the cross-sectional area of the coolant passageway and thus limit the volume of coolant that can be circulated through the cup per unit of time. This in turn, limits the ability of the coolant to absorb heat from the packing cup. It would therefore be desirable to provide means for eliminating the two piece construction of the prior art packing cup so that the O-rings could be eliminated to make room for a coolant passageway of larger cross-sectional area.
By means of my invention, these and other difficulties encountered using prior art packing case members or cups is substantially eliminated.